Siliceous Genus. 123 



cined, it does not effervefce, but becomes ge- 

 latinous. 



In a ftrong fire it melts ferfe into a whitijh 

 glafs. 



This ftone has been examined by Mr. 

 Margraaf only with a view of finding whe- 

 ther it contained copper. He found none, 

 but only calcareous Earth, gypfum, iron, and 

 filex. Mr. Rinman lately found it to contain 

 the fparry acid. 



SPECIES X. 

 Jade. 



Jade is found in fcattered maffes like peb- 

 bles, femi-tranfparent, of a greafy look, and 

 exceeding hard : its colour is either white, 

 grey, olive, green, or yellowiih : its fpecific 

 gravity from 2,97 to 3,389. According to 

 Mr. Saiiffure* it is fcarcely foluble in acids, at 

 leaft without particular management, and alfo 

 infufible in fire. However, he feems to have 

 paraded iron from it. 



May it not be a compound of filex and 

 jnagnefia ? 



SPECIES XI, 



